JP2691784B2 - Projection display device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a projection display device for enlarging and projecting an image formed on a liquid crystal light valve onto a screen, and more particularly to a non-polarized light source as an illumination light source for the liquid crystal light valve. The present invention relates to a projection type display device using a lamp that emits light.

[Prior Art] FIG. 7 is an explanatory diagram of an optical system of a conventional projection display device. In the figure, (1) is a light source, (120) is a lamp, and (1
Reference numeral 30 is a reflecting mirror, (2) is an illumination light flux emitted from the light source (1), (3) is a liquid crystal light valve, (8) and (9) are polarizing plates arranged before and after the liquid crystal light valve, and (4). ) Is a projection lens, (5) is a screen, and (10) is a condenser lens.

Next, the operation will be described. The light source (1) is a lamp (12
0) and reflector (130), liquid crystal light valve (3)
The illumination luminous flux (2) is applied to the. As the lamp, for example, a discharge lamp such as a metal halide lamp or a xenon lamp and a halogen lamp are used. An image is displayed on the surface of the liquid crystal light valve (3) as described later, and the in-plane transmittance changes according to the shade and color of the image. The light beam transmitted through the liquid crystal light valve (3) is further transmitted through the projection lens (4) to become a projection light (110), and is enlarged and formed on a screen (5) for viewing. The condenser lens (10) is provided in order to make the illumination light flux enter the projection lens with high efficiency and obtain a high-luminance projection image.

Next, the structure and operation of the liquid crystal light valve (3) will be described with reference to FIG. The liquid crystal (6) is sandwiched between two glass substrates (7), and polarizing plates (8),
(9) is arranged. In the case where no voltage is applied V = 0 (FIG. 8 (a)), the linearly polarized light (2a) transmitted through the incident side polarization plate (8) is polarized by the optical rotatory power of the liquid crystal when transmitted through the liquid crystal (6). Is rotated by 90 ° and the incident side polarization plate (8)
And the output side polarizing plate (9) arranged so that the polarization axes thereof are orthogonal to each other.
Through. On the other hand, when a voltage V equal to or higher than the threshold voltage Vth is applied (FIG. 8 (b)), the optical rotatory power of the liquid crystal becomes small, and the amount of light transmitted through the emission side polarization plate (9) increases as the voltage increases. Decrease.

A two-dimensional image display element can be formed by utilizing such a transmittance control action and further configuring electrodes in a two-dimensional array. The above liquid crystal is a TN with an optical rotation angle of 90 °.
(Twisted Nematic) An example of using liquid crystal in normally white mode was explained. As for the type of liquid crystal phase, the size of the optical rotation angle, and the like, as well known, other modified examples are known, but the description thereof is omitted because it is not directly related to the subject of the present invention.

Further, as a second conventional device, FIG. 9 shows an optical system of a device using three liquid crystal light valves. In the figure, (1) is a light source, which is specifically composed of a metal halide lamp, a xenon lamp, a halogen lamp or the like for generating white light, and a reflecting mirror (130).
(2) is an illumination luminous flux emitted from the light source (1), (14R), (1
4B) is a color separation dichroic mirror, (15B), (15
G) is a dichroic mirror for color synthesis, (11), (12)
Is a mirror, (3R), (3G) and (3B) are liquid crystal light valves, (8R), (8G) and (8B) are incident side polarization plates, (9R),
(9G) and (9B) are output side polarization plates, (10R), (10G),
(10B) is a condenser lens.

 Next, the operation of the second conventional device will be described.

The illumination luminous flux (2) is emitted from the white light source lamp (120),
The light is reflected by the reflecting mirror (130) and emitted from the light source (1). The dichroic mirror (14R) reflects red light and transmits blue and green light. The dichroic mirror (14B) reflects blue light and transmits green light. Accordingly, the liquid crystal light valves (3G), (3B), and (3R) are irradiated with green, blue, and red illumination light beams, respectively. Liquid crystal light valve (3G),
In (3B) and (3R), an image corresponding to green, blue, and red color light is formed by an external circuit (not shown), and the irradiation light is transmission-modulated within the light valve plane. Light emitted from the liquid crystal light valves (3G), (3B), and (3R) is combined by a dichroic mirror (15B) that reflects blue light, a dichroic mirror (15G) that reflects green light, and a reflection mirror (12). Incident on the projection lens (4) as
An enlarged color image is formed on the screen (5) as a projected light flux (110) for viewing. The condenser lenses (10R), (10G), and (10B) are used to make red, green, and blue lights incident on the projection lens (4) with high efficiency. Also, each liquid crystal light valve (3R),
The configurations and operations of (3G) and (3B) are the same as those described above with reference to FIG.

[Problems to be Solved by the Invention] Since the conventional projection display device is configured as described above, the luminous flux used for image display in the liquid crystal light valve is the incident side polarization plate (8) or ( 8R), (8G), (8
Only the linearly polarized light component selected by B). On the other hand, the lamp (120) used in the conventional device is a non-polarized (naturally polarized) light source such as a metal halide lamp, a xetano lamp, and a halogen lamp, and the illumination light (2) is also non-polarized.

As a result, the incident side polarization plate (8) or (8R), (8G),
When passing through (8B), only about half of the illumination luminous flux (2) was incident on the liquid crystal layer. The other half of the light energy is mainly incident side polarization plate (8) or (8R), (8G), (8
B) is absorbed and turned into heat, and the incident side polarization plate (8) or (8
R), (8G), (8B) temperature rise deterioration of polarization characteristics,
This has been a cause of fluctuations in liquid crystal operating characteristics due to temperature rise of the adjacent liquid crystal layer.

The present invention has been made to solve the above-mentioned problems, and effectively utilizes the energy of the illumination light flux, and further, the incident side polarization plate (8) or (8R), (8G), (8B) An object of the present invention is to obtain a projection display device capable of preventing temperature rise and consequently realizing high-luminance image display.

[Means for Solving the Problem] A projection display apparatus according to the present invention has a polarization splitting means for splitting an unpolarized light flux into first and second linearly polarized light fluxes and two reflecting surfaces orthogonal to each other. A third line rotated by 90 ° with respect to the polarization direction of the second linearly polarized light beam, the crossing line of the orthogonal reflecting surfaces being a direction of a reference angle forming 45 ° with the polarization direction of the second linearly polarized light beam. Of the first linearly polarized light flux, and a polarization rotation means that re-enters the polarized light splitting means as a linearly polarized light flux of And an optical path conversion means for making a fourth linearly polarized light beam having substantially the same traveling direction and polarization direction as the above, and illuminating the liquid crystal light valve with the first linearly polarized light beam and the fourth linearly polarized light beam. Is.

In other words, it has an optical means for converting an unpolarized illumination light beam emitted from a light source into a linearly polarized light, and is configured so that the polarization axis of the incident side polarization plate of the liquid crystal light valve and the direction of the linearly polarized light of the illumination light beam coincide with each other. It is a thing.

[Operation] By linearizing the illumination light flux as described above,
The amount of light transmitted through the incident side polarization plate is doubled, and the suction by the polarization plate can be reduced.

Further, when the extinction ratio of the illumination light beam linearly polarized by the optical means is good, the device can be configured without the incident side polarization plate.

[Embodiment] FIG. 1 is an explanatory diagram showing an optical system of a projection display apparatus in Embodiment 1. In the figure, (20) is a polarized light separating means and (21) is a polarized light rotating means, which is composed of two mirrors (21a) and (21b) orthogonal to each other. (twenty three)
Is an optical path changing means.

 Next, the operation of the embodiment will be described.

The illumination luminous flux (2) emitted from the light source (1) is in a non-polarized state as in the conventional example, and the joint surface (20a) of the polarization splitting means.
Therefore, it is separated into reflected S-polarized light (30) and transmitted P-polarized light (33a). The reflected S-polarized light enters the polarization rotating means (21). The polarization rotation means (21) has a line of intersection (22) z from the x direction in the drawing.
It was arranged so that it was rotated around the axis by 45 ° as a reference angle. It is composed of orthogonal mirrors (21a) and (21b), and has a function of rotating the polarization direction of incident light by 90 ° and emitting it, as described later.

Therefore, the S-polarized light (30) incident on the polarization rotation means
Is emitted as P-polarized light (31), and is output as polarized light separating means (20).
Is transmitted as P-polarized light as it is, is reflected by the optical path changing means (23), and is converted into linear polarized light (33b) having the same polarization direction and traveling direction as the transmitted P-polarized light (33a).
It is incident on the liquid crystal light valve (3) through 0). The polarization axis of the incident side polarization plate (8) of the liquid crystal light valve (3) is aligned with the direction of the incident linearly polarized light (33a), (33b). As a result, about twice as much light energy is incident on the liquid crystal layer as compared with the case where a conventional unpolarized light flux is incident, which contributes to image display. The light emitted from the liquid crystal light valve (3) is projected by the projection lens (4) as in the conventional example.
0), which is enlarged and projected on the screen (5).

Next, the operation of the polarization rotation means (21), which is a characteristic feature of the present invention, will be described in detail with reference to FIG.

2 (a) is a perspective view and FIG. 2 (b) is a plan view. The polarization rotating means (21) is composed of optical path changing means (21b) orthogonal to each other. Polarization rotation means (21)
The light ray (30) that is incident on the crossing line (22) is
It is a linearly polarized light (amplitude E ₁ ) forming 45 ° and is divided into quadrature components x ₁ and y ₁ of equal amplitude. However, the direction of y ₁ is the intersection line (2
I took it in parallel with 2). As shown in the figure, the mirror images of the x ₁ , y ₁ component reflected by the optical path changing means (21b) are sequentially x ₂ , y ₂ and x ₃ , y _3.
The direction is indicated by. y ₃ is in the same direction as y _1, and x
₃ is opposite to x ₁ .

Therefore, x, the reflectance of the y-polarized light is substantially equal x, when the phase difference of two conditions are satisfied that it is small at the time of reflecting the y direction of polarization, x _3, y ₃ are the same phase with equal amplitude Since it becomes a component, the polarized light E ₃ becomes a linearly polarized light orthogonal to E ₁ as shown in the figure. Similarly, the linearly polarized light (polarized light in the E ₁ direction) incident on the optical path changing means (21b) in FIG. 2 (a) is sequentially reflected by the optical path changing means (21b) and (21a), and becomes E ₁ It becomes a linearly polarized light which is orthogonal to each other.

As described above, in FIG. 1, since the S-polarized light (30) reflected by the polarization splitting means (20) is linearly polarized light that forms 45 ° with respect to the intersection line (22), the polarization rotating means (21 ), The light is reflected in the traveling direction opposite to the incident light in a state where the polarization direction is rotated by 90 °, becomes P-polarized light (31) and re-enters the polarization splitting means (20), and becomes the transmitted P-polarized light (32) as it is. And emits the polarized light separating means (20). The optical path changing means (21b)
In order to obtain a strongly reflected light (31), in addition to the above conditions, it is necessary that both the reflectance of polarized light in the x and y directions be high. As an optical path changing means satisfying these conditions, it is preferable that an optical multilayer film is formed on a glass substrate to realize desired characteristics. However, even a simple metal vapor deposition optical path changing means (for example, an optical path changing means in which Al, Ag, Cr, etc. are vapor-deposited on a glass substrate) or a metal plate optical path changing means has a degree of improvement over the above optical multilayer film optical path changing means. Although low, the effect of the present invention can be obtained. This is because the light ray (31) is converted into P-polarized light (32) when passing through the polarization separation means (20), and the light rays (33a) and (33b) have the same polarization direction.

[Other Embodiments] Next, a second embodiment of the present invention will be described with reference to FIG. In the figure, (23a) and (23b) are reflection optical path changing means. The non-polarized illumination light (2) emitted from the light source (1) is separated by the polarization splitting means (20) into reflected S-polarized light (33a) and transmitted P-polarized light (30). The transmitted P-polarized light enters the polarization rotating means (21).

Similar to the first embodiment, the polarization rotation means (21) is composed of orthogonal mirrors (21b) having an intersection line (22) in the direction rotated by 45 ° around the z axis from the x axis direction. Since the transmitted P-polarized light (30) forms an angle of 45 ° with the intersecting line (22), the polarization direction is rotated by 90 ° by the polarization rotating means (21) and the light beam (30).
And S-polarized light (31) traveling in the opposite direction. S polarization (31)
Is reflected S polarized light (32) by the polarization separation means (20), is reflected by the optical path conversion means (23a), (23b), and is linearly polarized light having the same polarization direction and traveling direction as the reflected S polarized light (33a). (33b) and enters the liquid crystal light valve (3) through the condenser lens (10). The polarization axis of the incident side polarization plate (8) is defined by the incident linearly polarized light (33
They are arranged in line with the directions of a) and (33b), and approximately twice as much light energy is incident on the liquid crystal layer as compared to the conventional case where unpolarized illumination light is incident, contributing to image display. To do. The light emitted from the liquid crystal light valve becomes projection light (110) by the projection lens (4) as in the conventional example, and is enlarged and projected on the screen (5).

Next, a third embodiment of the present invention will be described with reference to FIG. This embodiment is the same as the polarization separating means (20), the polarization rotating means (21) and the optical path changing means (23) of FIG. 1 showing the first embodiment.
Is an example in which is applied to the optical system of FIG. 9 showing a second conventional example. Similarly to the first embodiment, the light rays (33a) and (33b) are linearly polarized light having the same polarization direction and traveling direction.
The polarization axes of the incident side polarization plates (8R), (8G) and (8B) are arranged in the same direction as the polarization directions of the light rays (33a) and (33b). With the above-described configuration, the light energy loss due to the incident side polarization plate of the liquid crystal light valve can be reduced as in the first embodiment.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, the liquid crystal light valve (3) is included in the two linearly polarized lights (33a) and (33b) of FIG. 1 showing the first embodiment.
A wedge prism (50) is newly placed at a position closer than this. As a result, ray (33a) and ray (33
Each half-beam represented by b) is refracted in different directions with the center line (51) of the wedge prism as a boundary,
It becomes (52), and the same spot on the liquid crystal light valve (3) is overlapped and irradiated. Since the light paths of the light rays (33a) and (33b) are different from each other, it is feared that unevenness in brightness and color of the projected image may occur when the light rays are irradiated to another position on the liquid crystal light valve as shown in FIG. However, in the present embodiment, since the two half-beams are overlapped and illuminated, such a problem is solved.

Next, a fifth embodiment of the present invention will be described with reference to FIG.
In this embodiment, a positive cylindrical lens (55a) is newly added at a position before the liquid crystal light valve (3) in the two linearly polarized lights (33a) and (33b) of FIG. 1 showing the first embodiment. ), And a beam diameter adjusting optical system (55) consisting of a negative cylindrical lens (55b) is inserted. Light rays (33a), (3
3b) is converted into focused light by a positive cylindrical lens (55a),
By collimating again with the negative cylindrical lens (55b),
A light beam (58) having a reduced diameter in the z direction is obtained. Since the cylindrical lenses (55a) and (55b) have no lens effect on the light in the y direction, the luminous flux diameter in the y direction does not change. As described above, in the present embodiment, since the light flux diameter adjusting optical system (55) can independently change only the light flux diameter in the z direction, it is optimal depending on the size of the display area in the z and y directions of the liquid crystal light valve. It is possible to obtain an illumination light flux having a different cross-sectional shape. In particular, the cylindrical lens (55
Since the light beam 58 that has passed through b) becomes parallel again, by inserting the light beam adjusting optical system (55), the setting of the optical system in the subsequent stage is not affected, and the cylindrical lens (55b The separation distance between the lens) and the condenser lens (10) can be freely set. In order to enlarge the light flux diameter in the z direction, the order of the positive and negative cylindrical lenses may be reversed from that shown in FIG. Further, in order to make the optical system small, the known Fresnel lenses may be used to form the cylindrical lenses (55a) and (55b).

In each of the above embodiments, the case where the line of intersection of the orthogonal reflecting surfaces is set to the direction of the reference angle of 45 ° has been described, but it goes without saying that this angle has a degree of freedom. That is, if the angle of 45 ° is deviated by θ °, the polarization rotation means (21)
The polarized light (31) emitted from the device is deviated by 2θ °, but this deviated component is absorbed by the polarized light separating means (20), and the polarized light (32) emitted from the deviated component becomes a non-deviated polarized light. And the energy loss PL in this case is PL = {1
−COS ² (2θ)}, even if θ = 3 °, PL
= 0.0055, which is 1% or less, and in this sense, even if the value of the angle of 45 ° described in claim 1 has some degree of freedom and width,
It does not impair the identity of the invention described in the same paragraph.

Also, both are liquid crystal light valves (3) or (3
The case where the incident side polarization plates (8) of (R), (3G) and (3B) are used in the same manner as the conventional configuration has been described. However, since the light rays (33a) (33b) generated from the light flux (2) are linearly polarized light, the liquid crystal light valve (3) or (3R), (3
G) and (3B) are incident side polarization plates (8) or (8R) and (8
Images can be formed without using G) and (8B). The polarizing plate has optical loss due to polarization selection characteristics and absorption loss of the material itself. However, if the incident side polarizing plate (8) or (8R), (8G), (8B) is omitted as described above, the material Since the absorption loss can be eliminated, a projection display device with higher brightness can be realized.

Further, although each embodiment of the present invention uses a transmissive liquid crystal light valve, a projection display device using a reflective liquid crystal light valve is also known. A reflection type liquid crystal light valve is used as a linear polarization optical system including a polarization splitting means (20), a polarization rotating means (21), an optical path changing means (23) or (23a) and (23b), which are the core of the present invention. It can be applied to devices without problems. Further, in the above-mentioned embodiments, the liquid crystal light valve has been described by taking the system utilizing the optical rotatory power of the liquid crystal as an example. In addition to this, a system for electrically controlling the birefringence of the liquid crystal, for example, ECB (electrically controllable
The ed birefringence) type and the like are also known, and it goes without saying that the present invention can be applied to a projection type display device using a liquid crystal light valve that requires these incident side polarization plates.
Further, the number of light valves is not limited to three, and three or more, or one or two light valves can be applied without any problem.

[Effects of the Invention] As described in detail above, according to the projection display device of the present invention, the unpolarized illumination light flux emitted from the light source is converted into the linearly polarized light having the polarization direction to be incident on the liquid crystal light valve. Since the optical means is provided, the amount of light transmitted through the incident side polarization plate of the liquid crystal light valve is doubled, and a projected image with high brightness can be realized. Further, it is possible to reduce the deterioration of the polarization characteristics and the variation of the operation characteristics of the liquid crystal due to the heat generation of the incident side polarization plate, which have been problems in the past. Furthermore, by omitting the incident-side polarization plate of the liquid crystal light valve, which is conventionally required, the absorption loss of the material of the polarization plate itself is eliminated, so that a projection display device with higher brightness and simpler implementation can be realized.

[Brief description of the drawings]

FIGS. 1, 3, 4, 5 and 6 are explanatory views showing an optical system of a projection type display device in Examples 1, 2, 3, 4 and 5, respectively, and FIG. 2 is a projection type of the present invention. FIG. 7 is an explanatory view of the configuration and operation of the polarization rotating means used in the display device, FIGS. 7 and 9 are explanatory views of the optical system of the conventional projection display device, and FIGS. 8 (a) and 8 (b) are liquid crystal light valves. FIG. 3 is an explanatory diagram of the operation principle of FIG. In the figure, (3), (3R), (3G), and (3B) are liquid crystal light valves, (4) is a projection lens, (1) is light source means,
(20) is a polarization separation means, (21) is a polarization rotation means (23),
(23a) and (23b) are optical path changing means. In the drawings, the same reference numerals indicate the same or corresponding parts.

Front page continued (72) Inventor Eiichi Tode 1 Baba Institute, Nagaokakyo City, Kyoto Prefecture Electronic Product Development Laboratory, Mitsubishi Electric Corporation (72) Inventor Mitsushige Kondo 1 Baba Institute, Nagaokakyo Kyoto Prefecture Mitsubishi (56) Reference JP 61-122626 (JP, A) JP 62-100702 (JP, A) JP 63-197913 (JP, A) JP 3-157621 (JP, A) JP-A-3-191318 (JP, A)

Claims (2)

(57) [Claims] 1. An optical system comprising a liquid crystal light valve for forming an image, a projection lens for enlarging and projecting an image formed on the liquid crystal light valve, and a light source means for emitting a non-polarized light beam for illuminating the light valve. In a projection display device having: a polarization splitting means for splitting the unpolarized light flux into first and second linearly polarized light fluxes, and two reflecting surfaces which are orthogonal to each other, and a line of intersection of the orthogonal reflecting surfaces is A configuration in which the polarization direction of the second linearly polarized light beam is at a reference angle of 45 °, and the polarization direction of the second linearly polarized light beam is rotated by 90 ° to the polarization separating means as a third linearly polarized light beam. A polarization rotation means for re-incident light, and a light flux obtained by re-incident light of the third linearly polarized light flux to the polarization splitting means, having the same traveling direction and polarization direction as the first linearly polarized light flux. 4 linearly polarized light flux That is composed of the optical path changing means, the projection display apparatus characterized by illuminating the liquid crystal light valve by the first linear polarized light and the fourth linearly polarized light. 2. On the optical paths of the first and fourth linearly polarized light beams,
By inserting a light beam diameter adjusting optical system consisting of a positive cylindrical lens and a negative cylindrical lens at a position in front of the liquid crystal light valve, both linearly polarized light beams remain parallel,
2. The projection display device according to claim 1, wherein the diameter of the light beam in one direction perpendicular to the light beam axis can be adjusted.